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Discussion Starter #1
Hey all not sure if should put in the race section or here.I'm looking into doing an upgrade on the race motor of my old F4 750. so far we are leading the championship but the other guys are quick. I'm wondering if anyone has built a race motor and what specs have worked. Or seeing as apparently the SPR motor has around 15hp more what specs did they do to get that. I'm thinking of new pistons and rings, camshafts and some head work as well undercutting the gearbox and maybe I', thinking 1000 fuel injectors. Then where does everyone get their engine parts from? I'm having a lot of problems finding parts. I can get some standard stuff but thats all I've found
cheers:f4:
 

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SPR had hand finished intake ports and titanium valves for one thing. Cams and other parts are same, I think!?!
Big difference is the gearbox has some different ratios. Taller first and closer top 2 if memory serves...someone here knows for certain.
 

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King of Bling
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The SPR has a slightly different cylinder head design, with modified inlet tracks and redesigned combustion chamber.

The pistons are "MAHLE" with cooling oil jets, and the bores are coated with some slippery s**t that helps reduce friction .

The primary transmission has shorter ratios, and a slightly beefed up reinforced clutch. As Ed stated, the SPR comes with a close ratio gearbox with a stupidly long first gear ( as the SENNA ).

Be careful going down the SPR engine route, as parts for these motors are no longer available... Not even the head gasket, which became unavailable a couple of years ago.


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Discussion Starter #4
well cheers for that.. i found another thread somewhere that said the cams are bigger and yeah the heads ported differently. im really hoping to find some specs ie the cam grind angle and size of ports etc.. i probably wont bother changing my gearbox ratio as so far gearing is ok on the tracks.. just been altering my sprockets. We will do our own porting work, and if i can get the specs on cams ill just get a cam grinder to make me some.. just hoping to get a good point to start from..
 

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?

Gasket,

Cams and pistons are different

valves are the same

SPR intakes are polished

head gaskets are the same

cylinders are the same

I believe EPROMs are different

tranny ratios totally different

SPR
1. 14x37....2.642
2. 16x33....2.062
3. 15x27....1.800
4. 19x30....1.578
5. 23x33....1.434
6. 18x24....1.333

750
1. 13x38....2.923
2. 14x31....2.214
3. 18x32....1.777
4. 20x30....1.500
5. 22x29....1.318
6. 21x25....1.190

and 750 primary ratios are different than 910/1000/1078s so the clutch baskets are

different

I doubt you'll find anyone that will grind a stupid MV cam....... they are the only radial

valve engines made.......for a reason :stickpoke


:popcorn:
 

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John;

there is a mistake in the parts manual......

SPR intake valves have a reduced section (streamlined) between the head of the valve

and the stem that bears on the valve guide

the valve guides, keepers, retainers, seals and spring seats are all the same

the valves are interchangeable.......with a small loss of of performance using 750

valves in an SPR

:popcorn:
 

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King of Bling
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Noel

There's loads of mistakes in all the parts manuals... Dozens and dozens of errors.

I'll give you a quick example... Check the part number quoted for the lower triple fork clamp on Startwins parts finder web site.

Pay special attention to which Limited Edition models came with magnesium parts and which models didn't.

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Discussion Starter #10
all good info.. yeah i managed to track down that the spr has a different head the ports are in a different position and they are 2mm larger than a standard 750.. the cams on the spr are bigger lift longer duration, tho I am unable to find the specs.. I'll check that mob in NZ see what they have to say cheers knurl. I also found that info on the mahle pistons, and I cant find anyone who sells them, having said that I cant find anyone that sells standard pistons. Also the valves are titanium in the spr.. but again cant find actual sizes or if anyone finds them.. The eprom was different but thats no biggy as I use different eproms anyway.. so now I just need to find parts.. I'm thinking of just proting the head out a bit. ill call that mob in nz see if they do cams.. wondering if I need to go bigger injectors maybe that 1000 set up.. but im not an enginer by any stretch i just know how to twist a throttle well.. Ill see what others say.. knurl i emailed fast by faraci on their contact page as that was all i could find but havent heard back also havent heard back from mv factory either.. Wish theyd help me make their bike win a championship lol
 

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Discussion Starter #11
oh and yep I saw the taller first gear.. which is a total waste of time in my opinion. On the track first gear on standard 750 is already tall enough.. it's already slow off initial bite. I'm slowly getting the right revs and dialling take off in.
 
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